1. Field of the Invention
The present invention relates to a method and an apparatus for producing tire bead cores.
2. Description of the Related Art
Conventionally, tire bead cores are produced by using an apparatus that includes a winding drum comprised of a plurality of arcuate segments aligned in a circumferential direction of the drum, wherein each segment is radially movable and has an outer periphery formed with at least one circumferential groove, as well as a chuck arranged between the neighboring segments and having a pair of clamp jaws for clamping a leading end of a bead wire that extends in a tangential direction relative to said winding drum. A bead wire extending in the tangential direction of the winding drum is guided toward the clamp jaws in a translation manner, so that the leading end of the bead wire is moved to a position between the clamp jaws, where it is clamped by the chuck. The winding drum is rotated together with the chuck so that the bead wire with its leading end clamped by the chuck is helically wound in the circumferential groove as a plurality of layers, thereby forming a bead core having a predetermined cross-section. Finally, the segments are synchronously moved radially inwards, so as to reduce an outer diameter of the drum to a value smaller than an inner diameter of the bead core.
The bead core produced as above may suffer from a problem when it has not undergone a sufficient plastic deformation and there still partially remains an elastic deformation, that the leading end of the bead wire axially dislocated for some reason or other tends to protrude laterally from the bead core, exhibiting a significant radius of curvature. In order to avoid such a problem, it is proposed to subject the leading end of the bead wire to a plastic deformation in advance, to have a radius of curvature corresponding substantially to the inner diameter of the bead core. In this instance, due unavoidable non-uniformity of the of the bead wire material, an excessive deflection tends to occur at the leading end of the,bead wire causing dislocation thereof from the predetermined position. Thus, the translation movement of the bead wire alone may not result in a proper positioning of the leading end at a position between the clamp jaws.
For these grounds, one may consider it appropriate to supply a bead wire having a straight leading end, or without being subjected to the bending deformation, and cause a translation movement of the leading end to a position between the clamp jaws. However, such a process again involves a problem that the leading end of the bead wire tends to significantly protrude laterally from the bead core, whereby operators in tire factory may be subjected to injuries or, when the bead core is embedded in the product tire, the surrounding carcass layer may be damaged.